This invention relates to foamable pharmaceutical and cosmetic compositions.
Foams and, in particular, foam emulsions are complicated systems which do not form under all circumstances. Changes in foam emulsion composition, such as by the addition of active ingredients may destabilize the foam. There is therefore a need for a foam composition which provides desirable properties to the skin and can remain stable whilst accommodating a variety of active ingredients.
U.S. Pat. No. 6,126,920 (“the '920 patent”) discloses treatment of various skin diseases, and in particular, scalp psoriasis, using a foamable pharmaceutical composition containing a corticosteroid active substance, an aliphatic alcohol, water, a fatty alcohol, a surface-active agent, a propellant and a buffering agent. The foamable composition contains 40-90% w/w composition of an aliphatic alcohol. The '920 patent is typical of many compositions that use aliphatic alcohols in the foam composition. The alcohol promotes fast drying and thereby attempts to address the sticky feeling left by many topical formulations after application; however, alcohols, and in particular the methyl, ethyl and isopropyl alcohols preferred in the '920 patent, are defatting agents and may cause skin to become dry and cracked. U.S. Pat. Application Pub. No. US2004/0151671 provides pharmaceutical compositions in a pressurized container, comprising a quick breaking alcoholic foaming agent. U.S. Pat. No. 5,783,202 provides a pediculicidal mousse composition containing a pediculicidal agent containing (a) from about 0.1 to about 10% w/w of a pediculicidal agent (b) about 70 to about 97% w/w of a foaming agent, which is preferably a quick breaking alcoholic foaming agent; and (c) from about 3 to about 20% w/w of an aerosol propellant. U.S. Pat. No. 6,730,288 teaches a pharmaceutical foam composition including (a) an active ingredient; (b) an occlusive agent; (c) an aqueous solvent; and (d) an organic cosolvent; wherein the active ingredient is insoluble in water and insoluble in both water and the occlusive agent; and wherein there is enough occlusive agent to form an occlusive layer on the skin.
A few dermatological foam products are available on the market.
Olux™ Foam, produced by Connetics, Inc., contains clobetasol propionate. Each gram of Olux™ Foam contains 0.5 mg clobetasol propionate, USP, in a thermolabile foam, which consists of ethanol (60%), purified water, propylene glycol, cetyl alcohol, stearyl alcohol, polysorbate 60, citric acid, and potassium citrate. It is dispensed from an aluminum can pressurized with a hydrocarbon propellant (propane/butane). Luxiq™ corticostroid foam medication contains 1.2 mg betamethasone valerate per gram, in a vehicle, comprising ethanol (60.4%), purified water, propylene glycol, cetyl alcohol, stearyl alcohol, polysorbate 60, citric acid, and potassium citrate, and pressurized with a hydrocarbon propellant. Alcohol is known to impair the integrity of the skin barrier, dry the skin and cause skin irritation. The incidence skin irritation (burning, itching and stinging) as detailed the package inserts of the above mentioned products is very high (54%), probably due to the high alcohol content. Moreover, the respective incidence of skin irritation caused by the vehicle of these foams is 75%.
Thus, while alcohol is useful in solubilizing an active agent and enabling effective dermal penetration of an active agent is desirable, the development of a safe foam vehicle, which will overcome the evident skin drying and irritation caused by alcohol, is warranted.
Furthermore, foam compositions that possess a lesser degree of thermal sensitivity, thus being more useful for the treatment of large skin areas are desired.